Grameen Sampark Final April 0... - pmgsy

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Apart from the above, both faces of Rat Trap Bonded
Brick wall are checked with plumb bob, so both the
faces are uniform. As a result there is no necessity to
provide plastering. All that would be required is neat
cement pointing and patching on one edge of the
header course. Hence there will be additional savings in
plastering.
On completion of construction and curing the back
filling was done with, in layers by local earth of
Maximum Dry Density (MDD) 1.70 gms./cc. Then an
earth compactor was employed to roll and compact the
retained earth. The compactor was directed to start
rolling from about 1 m away from the retaining wall and
it came slowly towards the folded wall and went on
rolling moving over the corbelled shelves with full
capacity of vibration, which is equivalent to 36 M.T.
Observations
Through the wall was expected to fail severely, it did
not. The stretches where the relieving shelves were not
in existence, after repetition of about 3-4 cycles of full
vibration rolling the vertical joint at the junction of fold
on the pond side showed a line of crack which
propagated along the line of weakness of brick masonry.
The maximum width of crack was about 35 mm and it
appeared at about 7250 mm from GL i.e. at about at ½ of
height from GL. This clearly signifies that the failure was
due to intensity of rolling load to this enormous extent.
Not by virtue of back filling. The entire operation was
Grameen Sampark
video recorded. A selected portion of video recording is
attached with a soft copy of this document.
Progress of Field Tests
A good number of folded plates were then applied to
different locations of different projects as a cost effective
tool for different height of retentions also. All are
performing satisfactory till date. Some photographs are
attached.
In one instance folded plate has been applied to act as a
guide bank beside a rivulet, which converges and
passes through a narrow vented old culvert at the fag
end of a PMGSY road – Rukunpur Khalshipara to
Bangaljhi Ferry Ghat under Package No. WB/14/27.
The stretch of road at this point would get inundated in
every monsoon. Erosion was a predominant feature in
this stretch. The folded plate brick masonry structure
was used as a guide bank and it performed very well. It is
observed that the fins of the folds acted like small spurs
and the soil started depositing between the fins and
chances of erosion has been reversed.
Analysis of Economics
A cost estimate has been done for three types of
retaining wall 11.45 m. long to retain 1.5 m. high earth.
The types of wall chosen are as under: -
1. Folded plate Rat-Trap Bonded wall.
2. Standard Trapezoidal Brick masonry wall.
3. Standard Trapezoidal Plain Cement Concrete
(1:2:4)
The following table shows the comparative analysis of
the economics of the types of walls.
Type of Wall Cost / running meter
1. Folded plate “Rat-Trap Rs. 1781.25 / m.
bonded wall”
2. Brick masonry retaining Rs. 3498.54 / m.
wall
3. Plain Concrete (1:2;4) Rs. 5104.60 / m.
retaining wall